Method and apparatus for producing a molecular film with an adjusted density

An object of the present invention is to provide a technique that can adjust a molecular density of the film of functional molecules (e.g. DNA molecules), which is utilized for biochips such as DNA chip, to a desired degree efficiently and easily. The method for producing a molecular film with an adjusted density according to the present invention includes forming a molecular film and adjusting a molecular density. In the forming a molecular film, a molecular film composed of molecules is formed on a conductive substrate, wherein the molecule includes a region capable of binding to the conductive substrate at least in a portion thereof. In the density adjusting, a molecular density of the molecular film is adjusted by desorbing a part of the molecules which make up the molecular film from the conductive substrate.